Generally, wind turbines use the wind to generate electricity. The wind turns multiple blades connected to a rotor, which spins a rotor shaft that is connected to a generator through a gearbox for producing the electricity. The gearbox is used to step up (vis a high speed shaft) the inherently low rotational speed of the turbine rotor for the generator to efficiently convert mechanical energy to electrical energy, which is provided to a utility grid. Various types of electrical generators may be used in these wind turbines.
To accommodate the need for greater power from windfarms, individual wind turbine generators are increasingly being provided with higher power output capability. In general, to accommodate a higher power output, the power generating equipment including electrical generator, gearbox and controls become larger and heavier. However, the larger components are often subjected to increased loads (e.g., asymmetric loads) that result from wind shears, yaw misalignment, and/or turbulence, and the increased loads are known to contribute to significant fatigue cycles on the drive train components, i.e., the gearbox and/or the generator. Over time, the drive train components may become worn and/or damaged, and require repair or replacement.
For example, over time, the bearings which support the high speed shaft may become worn, wherein the gearbox assembly becomes less effective in transferring rotational energy to the generator. In some cases, the bearings fail, which results in damage to the bearing bores. With certain installations, the repair of the gearbox requires the entire nacelle, gearbox, and rotor to be removed from the wind turbine prior to removing the gearbox and repairing and/or replacing the damaged gearbox. This can be a costly and expensive exercise, particularly considering that the blades can be between 60 and 100 meters in length.
Accordingly, it is desirable to provide an economical and efficient system and method for removing and/or replacing drive train components, such as a gearbox, “uptower” without removing the rotor and/or the rotor shaft from the wind turbine.